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Using ‘sentinel’ plants to improve early detection of invasive plant pathogens
Fig 3
The optimal number of sentinel plants to include in the sample depends on the sample size, sample interval and the total number of sentinels in the population.
A. The effect of varying the number of sentinels included in the sample (NS) on the percentage change in EDP compared to the baseline level, in the case PS = 50, N = 50, Δ = 30 days. The number of sentinels in the sample for which the reduction in EDP is maximised (
) is indicated by the green circle. Black dashed line marks the baseline EDP. B. The optimal number of sentinels 
to include in the sample when PS = 50, as the sample size (N) and sample interval (Δ) vary. Solid black line marks the maximum possible number of sentinels that could be sampled at any time (min(PS, N)). Grey shading marks the unfeasible region in which NS exceeds this maximum. Green circle marks the case considered in A (PS = 50, N = 50, Δ = 30 days). C. The analogous figure to B, but with PS = 100 sentinels added to the population. D. The analogous figure to B, but with PS = 200 sentinels added to the population.
doi: https://doi.org/10.1371/journal.pcbi.1010884.g003